// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

/*

 * NOTE: This file is the modified version of xcolumn_bmod.c file in SuperLU

 * -- SuperLU routine (version 3.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * October 15, 2003
 *
 * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
 * EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program for any
 * purpose, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is
 * granted, provided the above notices are retained, and a notice that
 * the code was modified is included with the above copyright notice.
 */
#ifndef SPARSELU_COLUMN_BMOD_H
#define SPARSELU_COLUMN_BMOD_H

namespace Eigen {

namespace internal {
/**
 * \brief Performs numeric block updates (sup-col) in topological order
 *
 * \param jcol current column to update
 * \param nseg Number of segments in the U part
 * \param dense Store the full representation of the column
 * \param tempv working array
 * \param segrep segment representative ...
 * \param repfnz ??? First nonzero column in each row ???  ...
 * \param fpanelc First column in the current panel
 * \param glu Global LU data.
 * \return 0 - successful return
 *         > 0 - number of bytes allocated when run out of space
 *
 */
template<typename Scalar, typename StorageIndex>
Index
SparseLUImpl<Scalar, StorageIndex>::column_bmod(const Index jcol,
												const Index nseg,
												BlockScalarVector dense,
												ScalarVector& tempv,
												BlockIndexVector segrep,
												BlockIndexVector repfnz,
												Index fpanelc,
												GlobalLU_t& glu)
{
	Index jsupno, k, ksub, krep, ksupno;
	Index lptr, nrow, isub, irow, nextlu, new_next, ufirst;
	Index fsupc, nsupc, nsupr, luptr, kfnz, no_zeros;
	/* krep = representative of current k-th supernode
	 * fsupc =  first supernodal column
	 * nsupc = number of columns in a supernode
	 * nsupr = number of rows in a supernode
	 * luptr = location of supernodal LU-block in storage
	 * kfnz = first nonz in the k-th supernodal segment
	 * no_zeros = no lf leading zeros in a supernodal U-segment
	 */

	jsupno = glu.supno(jcol);
	// For each nonzero supernode segment of U[*,j] in topological order
	k = nseg - 1;
	Index d_fsupc; // distance between the first column of the current panel and the
				   // first column of the current snode
	Index fst_col; // First column within small LU update
	Index segsize;
	for (ksub = 0; ksub < nseg; ksub++) {
		krep = segrep(k);
		k--;
		ksupno = glu.supno(krep);
		if (jsupno != ksupno) {
			// outside the rectangular supernode
			fsupc = glu.xsup(ksupno);
			fst_col = (std::max)(fsupc, fpanelc);

			// Distance from the current supernode to the current panel;
			// d_fsupc = 0 if fsupc > fpanelc
			d_fsupc = fst_col - fsupc;

			luptr = glu.xlusup(fst_col) + d_fsupc;
			lptr = glu.xlsub(fsupc) + d_fsupc;

			kfnz = repfnz(krep);
			kfnz = (std::max)(kfnz, fpanelc);

			segsize = krep - kfnz + 1;
			nsupc = krep - fst_col + 1;
			nsupr = glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);
			nrow = nsupr - d_fsupc - nsupc;
			Index lda = glu.xlusup(fst_col + 1) - glu.xlusup(fst_col);

			// Perform a triangular solver and block update,
			// then scatter the result of sup-col update to dense
			no_zeros = kfnz - fst_col;
			if (segsize == 1)
				LU_kernel_bmod<1>::run(segsize, dense, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
			else
				LU_kernel_bmod<Dynamic>::run(
					segsize, dense, tempv, glu.lusup, luptr, lda, nrow, glu.lsub, lptr, no_zeros);
		} // end if jsupno
	}	  // end for each segment

	// Process the supernodal portion of  L\U[*,j]
	nextlu = glu.xlusup(jcol);
	fsupc = glu.xsup(jsupno);

	// copy the SPA dense into L\U[*,j]
	Index mem;
	new_next = nextlu + glu.xlsub(fsupc + 1) - glu.xlsub(fsupc);
	Index offset = internal::first_multiple<Index>(new_next, internal::packet_traits<Scalar>::size) - new_next;
	if (offset)
		new_next += offset;
	while (new_next > glu.nzlumax) {
		mem = memXpand<ScalarVector>(glu.lusup, glu.nzlumax, nextlu, LUSUP, glu.num_expansions);
		if (mem)
			return mem;
	}

	for (isub = glu.xlsub(fsupc); isub < glu.xlsub(fsupc + 1); isub++) {
		irow = glu.lsub(isub);
		glu.lusup(nextlu) = dense(irow);
		dense(irow) = Scalar(0.0);
		++nextlu;
	}

	if (offset) {
		glu.lusup.segment(nextlu, offset).setZero();
		nextlu += offset;
	}
	glu.xlusup(jcol + 1) = StorageIndex(nextlu); // close L\U(*,jcol);

	/* For more updates within the panel (also within the current supernode),
	 * should start from the first column of the panel, or the first column
	 * of the supernode, whichever is bigger. There are two cases:
	 *  1) fsupc < fpanelc, then fst_col <-- fpanelc
	 *  2) fsupc >= fpanelc, then fst_col <-- fsupc
	 */
	fst_col = (std::max)(fsupc, fpanelc);

	if (fst_col < jcol) {
		// Distance between the current supernode and the current panel
		// d_fsupc = 0 if fsupc >= fpanelc
		d_fsupc = fst_col - fsupc;

		lptr = glu.xlsub(fsupc) + d_fsupc;
		luptr = glu.xlusup(fst_col) + d_fsupc;
		nsupr = glu.xlsub(fsupc + 1) - glu.xlsub(fsupc); // leading dimension
		nsupc = jcol - fst_col;							 // excluding jcol
		nrow = nsupr - d_fsupc - nsupc;

		// points to the beginning of jcol in snode L\U(jsupno)
		ufirst = glu.xlusup(jcol) + d_fsupc;
		Index lda = glu.xlusup(jcol + 1) - glu.xlusup(jcol);
		MappedMatrixBlock A(&(glu.lusup.data()[luptr]), nsupc, nsupc, OuterStride<>(lda));
		VectorBlock<ScalarVector> u(glu.lusup, ufirst, nsupc);
		u = A.template triangularView<UnitLower>().solve(u);

		new (&A) MappedMatrixBlock(&(glu.lusup.data()[luptr + nsupc]), nrow, nsupc, OuterStride<>(lda));
		VectorBlock<ScalarVector> l(glu.lusup, ufirst + nsupc, nrow);
		l.noalias() -= A * u;

	} // End if fst_col
	return 0;
}

} // end namespace internal
} // end namespace Eigen

#endif // SPARSELU_COLUMN_BMOD_H
